Complexity analysis is a fundamental aspect of computer science that focuses on evaluating the performance of algorithms in terms of their time and space requirements. It helps in understanding how the execution time or memory usage of an algorithm grows as the size of the input increases. By categorizing algorithms based on their efficiency, complexity analysis aids in making informed decisions about which algorithm to use for a specific problem. This analysis often involves concepts such as asymptotic notation, worst-case scenarios, and average-case performance, providing a framework for comparing different algorithms effectively.